Health Library

Encephalitis

What is encephalitis?

Encephalitis is a term used to describe inflammation of the brain. This condition causes problems with the brain and spinal cord function. The inflammation causes the brain to swell, which leads to changes in the person's neurologic condition, including mental confusion and seizures.

What causes encephalitis?

The cause of encephalitis varies depending on the season, the area of the country, and the type of exposure. Viruses are the leading cause of encephalitis. Although vaccines for many viruses, including measles, mumps, rubella, and chickenpox have greatly lowered the rate of encephalitis from these diseases, other viruses can cause encephalitis. These include herpes simplex virus and rabies.

Encephalitis can also occur following infection by disease-carrying agents including ticks (Lyme disease), mosquitoes (West Nile virus), and cats (toxoplasmosis).

What are the symptoms of encephalitis?

Encephalitis often is preceded by a viral illness such as an upper respiratory infection, or a gastrointestinal problem, such as diarrhea, nausea, or vomiting. The following are the most common symptoms of encephalitis. However, each individual may experience symptoms differently. Symptoms may include:

Headache

Sensitivity to light

Neck stiffness

Sleepiness or lethargy

Increased irritability

Seizures

Skin rashes

Difficulty talking and speech changes

Changes in alertness, confusion, or hallucinations

Loss of energy

Loss of appetite

Unsteady gait

Nausea and vomiting

In severe cases, an individual may experience the following:

Loss of muscle power in the arms and legs

Double vision

Impairment of speech and/or hearing

Coma

The symptoms of encephalitis may resemble other problems or medical conditions. Always consult your doctor for a diagnosis.

How is encephalitis diagnosed?

The diagnosis of encephalitis is made after the sudden or gradual onset of specific symptoms and after diagnostic testing. During the examination, your doctor obtains a complete medical history, including your immunization history. Your doctor may also ask if you have recently had a cold or other respiratory illness, or a gastrointestinal illness, and if you have recently had a tick bite, have been around pets or other animals, or have traveled to certain areas of the country.

Diagnostic tests that may be performed to confirm the diagnosis of encephalitis may include the following:

Magnetic resonance imaging (MRI). A diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

Computed tomography scan (also called a CT or CAT scan). A diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general X-rays.

Blood tests

Urine and stool tests

Sputum culture. A diagnostic test performed on the material that is coughed up from the lungs and into the mouth. A sputum culture is often performed to determine if an infection is present.

Electroencephalogram (EEG). A procedure that records the brain's continuous, electrical activity by means of electrodes attached to the scalp.

Spinal tap (also called a lumbar puncture). A special needle is placed into the lower back, into the spinal canal. This is the area around the spinal cord. The pressure in the spinal canal and brain can then be measured. A small amount of cerebral spinal fluid (CSF) can be removed and sent for testing to determine if there is an infection or other problems. CSF is the fluid that bathes the brain and spinal cord.

Brain biopsy. A procedure performed to remove tissue or cells from the body for examination under a microscope; in rare cases, a biopsy of affected brain tissue may be removed for diagnosis.

Intracranial pressure monitoring (ICP). Measures the pressure inside the child's skull. If there is a severe brain injury, head surgery, brain infection, or other problems, the brain may swell. Since the brain is covered by the skull, there is only a small amount of room for it to swell. This means that, as the brain swells, the pressure inside the skull goes up. If the pressure gets significantly higher than normal, it can cause damage to the brain. People who have hydrocephalus or brain tumors may also have their intracranial pressure monitored.

Intracranial pressure is measured in two ways. One way is to place a small, hollow tube (catheter) into the fluid-filled space in the brain (ventricle). Other times, a small, hollow device (bolt) is placed through the skull into the space just between the skull and the brain. Both devices are inserted by the doctor either in the intensive care unit (ICU) or in the operating room. The ICP device is then attached to a monitor that gives a constant reading of the pressure inside the skull. If the pressure goes up, it can be treated right away. While the ICP device is in place, you will be given medication to stay comfortable. When the swelling has gone down and there is little chance of more swelling, the device will be removed.

Treatment for encephalitis

Specific treatment for encephalitis will be determined by your doctor based on:

Your age, overall health, and medical history

Extent of the condition

Your tolerance for specific medications, procedures, or therapies

Expectations for the course of the condition

Your opinion or preference

The key to treating encephalitis is early detection and treatment. A person with encephalitis requires immediate hospitalization and close monitoring.

The goal of treatment is to reduce the swelling in the head and to prevent other related complications. Medications to control the infection, seizures, fever, or other conditions may be used.

The extent of the problem is dependent on the severity of the encephalitis and the presence of other organ system problems that could affect the person. In severe cases, a breathing machine may be required to help the patient breathe easier.

As you recover, physical, occupational, or speech therapy may be necessary to help regain muscle strength and/or speech skills.

The health care team educates the family after hospitalization on how to best care for the patient at home, and outlines specific clinical problems that require immediate medical attention by his or her doctor. A person with encephalitis requires frequent medical evaluations following hospitalization.